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Four-legged snake fossil wasn't a snake after all, scientists contend

A new study says the "controversial specimen" was actually a very long marine lizard.

This illustration shows what the four-legged fossil -- which a team of scientists now says is a marine lizard and not a snake -- might have looked like.
Julius Csotonyi

Four tiny little legs rocked paleontology in 2015 when researchers published a study in Science on a very unusual fossil. The 110-million-year-old fossil from Brazil showed a creature with a long sinuous spine and startling legs. It was hailed as the missing link between lizards and snakes, but a new study aims to debunk that interpretation.

"There are many evolutionary questions that could be answered by finding a four-legged snake fossil, but only if it is the real deal. The major conclusion of our team is that Tetrapodophis amplectus is not in fact a snake and was misclassified," paleontologist Michael Caldwell said in a University of Alberta statement on Thursday.  

Caldwell is the lead author of a paper on the fossil published in the Journal of Systematic Palaeontology. The research team reassessed the animal's anatomy and traced the fossil to a Cretaceous-period group of marine lizards called dolichosaurs.

Tetrapodophis amplectus has been reassessed and may not be a snake after all.

David Martill/University of Portsmouth

Part of what makes the fossil tricky is the way the rock split around it when it was discovered. The skeleton and skull ended up on one side while the other side had a mold of the animal. "The original study only described the skull and overlooked the natural mold, which preserved several features that make it clear that Tetrapodophis did not have the skull of a snake -- not even of a primitive one," Caldwell said.

The University of Alberta described the fossil as a "controversial specimen." Even if it's not a snake, it's still worthy of more study. The paper highlights how unusual Tetrapodophis amplectus is, calling it "a unique kind of lizard... with unexpected and fascinating morphologies not seen in other lizards."